When using the air washer for dehumidification, the spray water temperature must be:

In the context of using an air washer for dehumidification, the spray water temperature being cooled below the dew point is essential for effective moisture removal from the air. When air is cooled below its dew point, the moisture present in the air condenses into liquid water. This process is crucial for dehumidification because it allows for the efficient capture of excess humidity, making the air dryer.

If the spray water temperature is at ambient air temperature, it would have inadequate cooling effect, thus failing to facilitate condensation of moisture from the air. Similarly, if the water is heated above frost temperature, it does not aid in pulling moisture from the air, as warming the air causes it to retain more moisture. Moreover, while having the spray water temperature at least 5°C lower than the air temperature can aid in dehumidification, it may not be sufficient to reach the necessary level of cooling that brings the air below its dew point.

Therefore, maintaining the spray water temperature cooled below the dew point is a critical factor in managing humidity effectively with an air washer.